Generally, heterogeneous communications systems are those in which low power nodes (LPN), also commonly referred to as low power cells, femto cells, pico cells, relay nodes, hot spots, home enhanced NodeBs (HeNB), and so on, are placed throughout a macro cell layout. The LPNs may transmit/receive transmissions in the same spectrum as the macro cells in the macro cell layout.
The macro cells are conventional base stations that use a dedicated backhaul and are open to public access. They typically transmit at relatively high power levels, for example, at about 43 dBm. Pico cells are LPNs that also use a dedicated backhaul and are also open to public access but have lower transmit powers (typically 23-30 dBm) and are lower cost. Femto cells or HeNBs are consumer deployable base stations that use the consumer's broadband connection as the backhaul and may or may not have restricted association (as a closed subscriber group or CSG, for example).